George Perry is the coach and director of the Austin Track Club, a team of professional middle-distance runners in Austin, TX. He regularly integrates emerging sports & fitness tech into his coaching, providing real-world feedback and insight to product developers as well as contributing product reviews and use cases to SportTechie. George has no financial interest or commercial relationship with BSX Athletics.
Anyone fleetingly familiar with exercise science will tell you that endurance sports are full of pricks that generate an alarming amount of bio waste. BSX Insight 1.0 overcame this pain point – literally, a “pain” “point” – by developing a non-invasive lactate threshold test. BSX’s optical sensor embedded in a calf sleeve has enabled thousands of athletes to determine their lactate threshold and associated training zones without the need for needles, blood and rubber gloves.
BSX 2.0, currently in beta-testing, measures muscle oxygenation (SmO2). While everyone has at least heard of lactate and knows (or thinks they know) what it means for their workout, incorporating SmO2 into your training is more like a choose-your-own-adventure novel. And that’s exactly why BSX thinks muscle oxygenation may be the next great training metric.
You can’t manage what you don’t measure.
We often talk about an athlete’s training output in terms of pace, watts, reps, total load and bar speed. We carefully measure and manage these outputs because, well, we can. As far as the athlete’s body is concerned, though, these are mere stimuli. The athlete’s adaptations to training – the physiological processes that will ultimately make him bigger, faster or stronger – are the responses.
5 x 3 back squats at 315, 6 x 400 meters in 58 seconds, some notes and observations… standard training log fodder tells us what the athlete did with the stimuli. Outside of heart rate, we do not know what the stimuli did to the athlete. This absence of direct physiological feedback limits a coach’s ability to impose the precise stimuli that will induce the desired adaptations leading to maximum performance.
BSX 2.0 shares with its predecessor an insight into the athlete’s response. SmO2, like blood lactate, reveals how the body reacted to the stimuli.
BSX 2.0 Case Study: Running and Resistance Training To test things out we had Shane Niksic, a NCAA Division II All-American now in his first year with the Austin Track Club, wear the BSX sleeve for two weeks of tempo runs, hill repeats and resistance training. His resistance work included 1RM testing for the back squat and deadlift, and two sessions on an ARX unit. Running Response For the first few workouts we had Shane pull on the calf sleeve a few minutes before starting his tempo run or hills. Not until we did a progression run that went directly into hill repeats – and therefore Shane wore the sleeve for the entire time – did we see what we had been missing. The SmO2 curve revealed a distinct pattern in the warmup process. SmO2 gradually increases for the first 10 minutes of the warmup run, then spikes and plateaus 5-6% higher than the initial pre-activity level. About 5 minutes later SmO2 shoots up again, this time by ~4%. SmO2 is then relatively constant for the remainder of the warmup.
If you think of the warmup as a rocket launch-style sequence to bring all systems online, BSX 2.0 showed us when muscle oxygenation is a go. Coaches can plan and evaluate a workout – or any portion of a workout – in terms of how SmO2 changes from the “warmed-up” baseline. During intervals, the SmO2 curve indicates how much the athlete recovers between each interval. The closer SmO2 approaches the warmed-up SmO2, the more the athlete has recovered. Coaches can then manipulate the recovery periods to maintain the athlete above or below a given SmO2 to simulate race conditions, to induce a stronger or more specific adaptive response. BSX 2.0 has a high cross-over value from endurance sports to speed & power sports, which require a high level of anaerobic conditioning. By ensuring that SmO2 returns to baseline in between training intervals, coaches can be sure that the athlete is repeatedly stressing anaerobic systems and not transitioning into aerobic metabolism.
BSX 2.0 can supplement common subjective measures of effort. As an athlete progresses through an interval workout, you will likely see the same minimum SmO2 for each interval. During the last few intervals, the local SmO2 may get lower as the accumulation of fatigue requires the athlete to exert more effort to execute a given pace. This would ordinarily be noted by observing the athlete’s posture, breathing patterns or asking them to report their rate of perceived exertion (RPE). The slope of the minimum SmO2 across the intervals is a measure of the athlete’s accumulated fatigue, and should correlate with the athlete’s RPE. Likewise, the local maximum SmO2 between each interval illustrates how efficiently and how fully the athlete recovers between each segment. A downward slope across local max SmO2 may correlate with lactate accumulation or by-products that contribute to fatigue.
Resistance Response
The Adaptive Resistive Exercise (ARX) machines use a drive belt system attached to a 1.5-horsepower motor to induce maximum eccentric contractions in every rep (if you think 1.5 hp sounds kinda light, well, (a) you’re wrong, and (b) units with 3 hp motors are already being delivered). With two machines and a wide variety of belt configurations and body positions, the ARX can be adapted for a range of exercises including squats, pull downs, chest presses, leg presses and rows.
Shane performed two sessions one week apart. Each session consisted of belt squats, pull-downs and leg presses. He performed each exercise until he was unable to attain 70% of his maximum force output, which occurred on the 7th or 8th rep. Interestingly, his lower body exercises lasted about 2 minutes, a sport-specific duration for a middle-distance runner.
The minimum SmO2 for each session occurred during the belt squats. During the second session of belt squats Shane generated 17% more peak force and 28% more total force output compared to the first session, likely due to the neuromuscular learning of the first session. His minimum SmO2 decreased accordingly, reaching 71% for several reps during the second session compared to a minimum of 76% in the first session. By contrast, during a 1-repetition maximum (1RM) test for the back squat his SmO2 only reached 76%. This highlights the difference in what “maximum output” means when performing eccentric exercises, as with the ARX, compared with standard concentric-focused free weight routines.
The data revealed a super-compensatory SmO2 response during each set of pull-downs, similar to what we observed in the 2-3 minutes following the conclusion of the running workouts. This indicates one possible mechanism for why complementary or contrasting exercises have such a powerful effect on between-set recovery and the overall training stimulus when performed as an active recovery after sets of a “core” lift.
Extending Real-Time Data Beyond Endurance Sports
BSX Insight launched their first product in response to a well-defined, well-known need in endurance sports. At the time, co-founder Dustin Freckleton said the next step for the company would be delivering data that gives a real-time glimpse into what is happening inside the exercising muscle. BSX 2.0 does just that via SmO2, enabling the device to expand beyond endurance sport testing into being a regular tool for strength & conditioning in speed, power and team sports. As with many other sports wearables, only after the product is in full release and the data and use cases start pouring in will we begin to see the full value of SmO2 for sports training.